Counting ring utilizing cold cathode tubes



Sept. 1, 1953 T. s. MEDEROS, JR

COUNTING RING UTILIZING cow CATHODE TUBES Filed Dec. 22, 1950 lNVENTOR THOMAS 5. MEDEROSJR 9241 d. 7% ATTORNEY Patented Sept. 1, 1953 COUNTING RING UTILIZING COLD CATHODE TUBES Thomas S. Mederos, Jr., Granby, Conn., assignor to Underwood Corporation, New York, N. Y., a

corporation of Delaware Application December v2.2, 1950, Serial No. 202,303

1 Claim.

This invention relates to counting rings and more particularly to counting rings in which cold cathode gas filled tubes are used.

Counting rings using hot cathode vacuum or gas filled electron tubes are well known but have the disadvantage of complexity and use large amounts of energy to keep the cathodes hot. Such tubes must in general maintain a negative bias on the control elements to prevent tube conduction thus requiring a source of negative voltage or dissipation of a part of the high voltage supply in a voltage dropping resistor in the cathode leads. Additional complexity and power dissipation is incurred in providing filament power to keep the cathodes of all tubes heated during periods when all tubes but one are idle.

The use of cold cathode gas filled tubes is desirable in such a circuit for there are no filaments to be heated and the control elements must be energized by a positive voltage before the tube will be rendered conductive, thus eliminating many parts required for the hot cathode tube type of ring circuit and greatly reducing the heat generated by such a ring.

Counting rings of electron tubes have been used heretofore in counting circuits, in frequency divider circuits and for other similar uses. The ring circuit herein disclosed may be used for any such purpose and is not limited in uses to any specific application.

It is an object of the present invention to disclose a ring of sequentially operable cold cathode tubes with advantages as above set forth.

It is a further object to provide a ring of cold cathode gas filled tubes which may be rendered conductive seriatim in response to electrical pulses and which may be set at any desired starting point.

Other objects willbe set forth in the followin description of a preferred embodiment of the invention.

The accompanying drawing discloses a preferred form of the novel circuit.

The ring circuit herein described is of the type in which one tube is conductive at all times and in which application of a voltage pulse to an input lead causes the next tube in the ring to be-' come conductive and extinguish the preceding tube. Such operation is repeated for each ap plication of a pulse to the input circuit and causes the tubes to become conductive sequentially around the ring.

Referring to the drawing, the circuit of the present invention comprises a number of cold cathode gas filled electron tubes II] which in the actual circuit are OAA-G tubes.

two or more.

with current through a voltage dropping resistor it connected between the common plate lead 12 and the positive lead i l of a source of direct. current.

Each cathode l5 of the tubes to is connected to a ground lead it which is the negative side of the direct current source through a pair of resistors ii it in series and a condenser H9 in parallel with the resistors I! and 18.

The control element or grid 20 of each tube [0' is connected through a resistor 2| to the junction point of the resistors H and it in the cathode circuit of the preceding tube H). In the drawing, the mid point A of cathode resistors ii and it for tube 50 of thelast or N stage is returned to connect with lead A connected to grid resistor ii! for the first or 0 stage to make the circuit completely symmetrical in all stages. Condensers 22 are each connected on one Side to a grid 26 of a tube It and on the other side to a common control lead 23. This lead 23 is connected to a source of positive voltage pulses and, when pulsed, controls the start of conduction in the tube l0 following the one which is conducting when lead 23 is pulsed.

Connected between the positive voltage lead it and ground lead It are a pair of resistors 25 and 25 so selected that the voltage at their junction point with respect to lead It is more than the voltage required to be applied to grid 20 to start conduction in a tube I0. Each grid 24) is connected through an associated normally open switch '25 to the junction point of resistors 2t and 25.

In operation, assuming that no tubes it are conducting and a suitable D. C. voltage is applied between leads M and it, any desired tube it may be made conducting by closure of the switch 26 in its grid circuit. Closure of such switch 26 will apply voltage to grid 20 to ionize the gas in the selected tube l0 and start a discharge between cathode l5 and plate ll of that tube. This discharge will continue when switch 26 is opened, it being characteristic of the type of tube used that the grid 20 loses control of the discharge once it has started.

When any tube Ill has been started conducting as above set out, the voltage at its cathode I5 arises to a positive value due to the voltage drop in resistors l1 and I8. A portion of this The number of tubes used will be determined by the application: in which the circuit is to be used and may be: The plates ll of all tubes It are connected to a common lead l2 and are supplied voltage is applied through resistor 2| to the grid 28 of the adjoining tube In to the right. The voltage applied to this grid is not however enough to start conduction in this next tube II] but is of the order of 5'0 to 75 percent of the required value.

The ring of tubes in are now readyto-berendered conducting seriatim around the ring in response to positive pulses applied to control lead 23. Each positive pulse is applied through condensers 22 to the control electrodes 20 of all tubes but is of a voltage less than that required :tO start conduction in a tube H], the voltagebeing again in the approximate range of 5 0 to'7,5 percent of the control voltage,;requiredzfor. rids 20. Assuming that tube NJ in the 0 stage is conducting current, tube in stage ,1 is primedbyhaving a positive voltage applied to its grid 20 from the junction of resistors I! and [8 of stage l0 through resistor 2 I. Upon application of a pulse to control lead 23, all grids 20 are made .more positive but only in stage .1 will the grid 26 be raised to a firing potential by the combinedefiect of the initial voltage and the voltage impressed thereon froincontrol lead .Z3.an d tube M) of stage 1 will then start conducting.

In gas filled tubes of this type, the voltage dro across the tube is practically constant and is substantially independent of the current through the tube. The cathode of tube 10 in stage 1 is initially at 0- volts and because .of-condenser l9 and resistors IT and L8, when this tube starts conducting, its cathode potential does not increase sharply but only at a relatively slow rate. Since the voltage drop across the tube is constant, the anodevoltage on all anodes l ltdrops sharply when the tube 1.0 starts conducting to the value of the voltage drop across the tube and then increases as theicathode voltage rises.

At the instant of firing of tube-I0 .of stage 1 the tube ii] in stage 0 has itscathode at an appreciable positive voltage. This voltage likewise cannot change sharply due to the condenser 1-9 and resistors IT and 18in itscircuit. As a result, when tube It in stage 1 star-ts conducting and lowers the anode voltage, the voltage across tube ii) of stage 0 is not sufficient to maintain conduction and the tube will cease .to pass current.

Thering of tubes Ill are now conditioned for another pulse on lead 23 which will causea shift of the discharge from the newly fired tube Hl'to the next one on the right which now has a priming potential applied to its .grid 20. Inthis manner the discharge may be shifted around the ring of tubes 50 in response to positive voltage pulses applied to lead 23.

If the counting ring is to be used ina frequency dividing circuit, any. cathode lead may be used as the source of the lower frequency pulses and the number of tubes 10. in the ring will be determined by the extent of frequency division required.

When the countingring'isto be used tocount the number of inputpulses, it may be usedin conjunction with a magnetically or electrically operated counter in. which case. the counter would be controlled from-the plate or cathode lead of one .of the tubes 10 preferably thatcf the stage designated 0 or the ring may be used with similar rings to provide a, completely elsetronic counter in which counter the control lead 23 of each order may be coupled to the cathode I5 of the tube [0 of stage 0 of the prior order or at some point along the cathode resistors I1 and lfl atzwhich arcontrol voltage'oftheeorrect mag- :nitude isaavailable.

If it is desired to indicate which tube It of the zring is conductive at any time, the tube itself may be made visible since a conductive tube is illuminated, -a small neon bulb may be inserted across-the cathode resistors I1, 18 or a relay may "belinsertedinithe cathode circuit of each of the ztubes ilfl itD control a visible indicator.

in a representative circuit the values of the circuit components may be, using -OA4-G tubes for tubes l1! and with a voltage of 165 volts D. C. undead k4.

The above description of a preferred embodiment offlm yinvention is not to 'be taken in a limiting sense'as many variations are possible, all coming within the scope of the following claims.

What iscla'imed' A counting .circuit'compr'ising a plurality of electron conducting gas filled tubes, said tubes including an anode, a control element, and a cathode capable of electron emission without an application of external heat, a source of direct current to-energize said tubes, a common resistor between the positive side of said source and the anodes .ofialllsaid' tubes, a pair of resistors in series and a condenser connected between each cathode andthe negative side of .said source, a pulse supply circuit, a resistor and a condenser connectedto each control element, all said control relementlcondensersbeing connected .at their other terminals to said pulse supply circuit and each resistor connected to the junction of said cathode circuit resistors of an electrically adjacent tube whereby .a portion of the cathode voltage. of any conducting tube is applied to the grid of another tube, ast'arting conductor having a positive voltage-and a plurality of normally open switches, each switch connected between a control elementofiatube and the starting voltage conductor, closureof Yanyswitch causing the associated tubeto become conducting THOMAS .S.--IVLEDEROS, JR.

References 'Citeddn' the'fll'e of this-patent UNITED STATES PATENTS FOREIGN PATENTS Cmmtry;

I 9=0.1 mfd. 2'2 -mmfd.

Number Number Date Great-Britain Dec; 13, 1946- 

